A great many azo dyestuffs have been proposed over the past century which contain sulfonic acid substituents. Such dyestuffs have traditionally found application as acid dyestuffs for woolen fabric materials. Although extensive research has been conducted in this area of dyestuff chemistry over the past century, recent demands for dyestuffs with specific properties applicable to new fabric materials has rendered most of such early dyestuffs inapplicable to modern needs. As one example of a specialized area of dyestuff application may be mentioned carpet dyeing. In the dyeing of carpets it is necessary to provide a dyestuff with excellent "transfer". The transfer properties of a dyestuff relate to their ability to produce level dyeings even in heavy carpets and with filaments of a large diameter. Nylon carpeting represents a prime example of such a material which requires dyes of excellent transfer properties. Other problems occur in the dyeing of nylon carpeting which are occasioned by variations in the carpeting itself: for example, nylon carpeting may have localized areas of differing crystrallinity, due perhaps to differing stresses established in the cold drawing to which the fiber is subjected during manufacture. Such localized areas accept the acid dyes at different rates and in varying amounts, depending upon the physical characteristics of the carpet in each area. With a dyestuff of excellent transfer properties, it is possible to dye the carpeting with an evenness not possible with dyestuffs lacking such transfer properties. In addition to transfer properties, fastness to light is also an important consideration.
I have discovered a new series of acid dyes which dye polyamide fiber material, in particular carpet material, in shades ranging from bright canary yellow to rich golden yellow. The dyeings are characterized by outstanding lightfastness and transfer properties.
Acid dyes made from an N-alkyl-N-phenylbenzylamine coupler have been reported in the past, but none of these contain a sulfamyl group in addition to a sulfonic acid group. Among the known structures are C.I. 13150, which is 2,5-dichlorosulfanilic acid coupled into N-ethyl-N-phenylbenzylamine. Similar dyes listed in the Colour Index are C.I. 13145, C.I. 13155, C.I. 13160, C.I. 13165, C.I. 13170, C.I. 13175, C.I. 13180, and C.I. 13185. A series of heterocyclic dyes made by coupling a heterocyclic base into an N-alkyl-N-phenylbenzylamine containing a sulfonic acid group are reported in published Japanese Application No. 72/05757.
Disperse dyes containing a sulfamyl group, made by coupling a diazotized aminobenzene into an .alpha.-(N-alkylanilino)-m-toluenesulfonamide, are reported in U.S. Pat. No. 3,685,952 of Edgar E. Renfrew. These dyes are water insoluble, contain no sulfonic acid groups and are suited primarily as dyes for polyester fibers rather than polyamide material.